I have refered some forums and had taken the precausion not to repeat those mistakes.

include "/opt/zimbra/openldap/etc/openldap/schema/core.schema"
include "/opt/zimbra/openldap/etc/openldap/schema/cosine.schema"
include "/opt/zimbra/openldap/etc/openldap/schema/inetorgperson.schema"
include "/opt/zimbra/openldap/etc/openldap/schema/amavisd.schema"
include "/opt/zimbra/openldap/etc/openldap/schema/zimbra.schema"
include "/opt/zimbra/lib/conf/zimbra-ext.schema"
include "/opt/zimbra/openldap/etc/openldap/schema/nis.schema"
include "/opt/zimbra/openldap/etc/openldap/schema/samba.schema"